FR2757419A1 - Evaporator concentrating e.g. grape must solution rapidly under vacuum - Google Patents

Abstract

This method concentrates a solution by evaporation and sequentially, the solution passes through a succession of evaporators (effects) under vacuum, in a dispersed state. The fluid is constrained to travel as thin layers over the hot internal surfaces in the turbulent flow regime, for a most intensive evaporation of water or other solvent substance. Preferably the fluid passes vertically down through a series of elliptical, evacuated chambers with rotary fluid distributors, which set up the required conditions.

Description

 The claimed invention relates to the problem of the concentration of sensitive solutions, by evaporation under vacuum and until high concentrations are obtained, without however reaching the pasty state.

This task is generally entrusted to two types of apparatus: the first, often of the "falling flow" type, with one or more effects, which brings the concentration up to 40
Brix approximately, (beyond, the uniformity of the film descending by gravity in the tubes, becomes difficult); the second, which has a function of "finisher", is of the type with the single tube, vertical, with a single passage of the product , which crosses it by describing a helical trajectory, under the action of a variable speed rotor.They are already numerous on the market; they are similar in principle, and have in common a vertical tubular body, heated by steam or hot water, circulating in peripheral liners.

They are different by the central rotor, which conditions the distribution of the treated product, in its fall along the tubular wall. For "LUWA" devices, the rotor blades do not touch the surface of the tube. They pass over their entire length of a few tenths of a millimeter from this surface which is rectified, causing the formation of a film which flows in turbulent regime in the form of a spiral, up to the lower collector.

 For the devices "BAYER", "SAMBAY", and others, the blades of the rotor touch the tubular wall, by means of light "scraping" elements, which are articulated over the entire length of the blades, and which apply to the surface, under the stress of centrifugal force.

 The device object of our invention is a variant of the above devices, closer to "LUWA" of which we attach an illustration in the appendix. The product enters (l) .in the heated body (2) and descends in sorted mlnce spiral towards the outlet (4); the vapor rises in the center, sucked out, exits at (5) after being purified by the droplet separator (coolant fluid bugle enters at (7) and exits at (8), delta jacket.

 The present invention relates to an evaporator with a vertical body, consisting of a series of concentric, len ticular, chambers, arranged one on top of the other and interlinked by a large central, circular opening. , reminds a little of a bellows of expansion; it is arranged in a jacket where circulates 1 water, or the fluid, of heating.

 A axis concentric with the above-mentioned enclosures and arranged over the total height, supports a series of mini-turbines, fixed opposite each of these lenticular enclosures, slightly above their median plane. The assembly is actuated by a gear motor.

 In the upper part of the evaporator, fixed to the body described above, an expansion and retention chamber for drops, is connected by a large diameter conduit, to the condenser and vacuum pump device.

 In the lower part, a cylindrical tank provided with a heating jacket, collects the concentrated liquor, which is kept at constant level by admission of weak liquor. A circulation pump connected to this tank rises the liquor to the base of the chamber expansion, from where it flows into the central body described above.

 In its fall the liquid flow is taken up, at the level of each lenticular enclosure, by the centralized mini-turbine and projected onto the hot walls, on which it slides to a scraper device made up of nylon threads fixed between each turbine and rotating at the same speed.

The turbulence of the flow is thereby increased and therefore the transmission coefficient, especially for very concentrated solutions. These wires apply to the walls under the action of centrifugal force, bending according to their shape and the viscosity of the solution.

 The extraction of the concentrated liquor is done by a variable speed pump, which allows to control the recirculation and by the same, the final concentration.

The invention is shown in the accompanying drawing,
which illustrates, schematically, in section, an embodiment of this type of evaporator.

 Let us observe that it is very different from the devices that the LUWA, BAYER, SAMBAY, etc. build, whose body is internally constituted by a perfect cylindrical surface, while in our case it is divided into multiple enclosures of elliptical section. .

 The evaporator can be divided into 4 parts, which are, following the order of the previous presentation - the body (A), composed of a series of superimposed and interconnected speakers, which are surrounded by a jacket where circulates the heat transfer liquid, generally water; - the central axis (B), provided with turbines, actuated by its upper end and resting at its lower end on a bearing in abutment; - the vapor expansion chamber and the retention of entrained drops (C); - the tank (D) for collecting and reserving the liquid to be concentrated, with its temperature maintenance jacket.

 The liquid to be concentrated enters the evaporator, sucked up by the vacuum, in (l), through a valve controlled by a level detector, intended to keep it constant in the tank. pump (2), which injects it at the base of the chamber (C) .I1 falls on the first turbine (3), which disperses it in fine drops, projected onto the hot surface of the enclosure (4); flows in a thin layer, scraped by the elastomer threads (5), passes through the opening to the next enclosure, after a first concentration; others follow.

 The above sequence is repeated at each of the speakers, up to the collection tank (D). An extraction pump is connected e (o). Vapors rise in the expansion chamber (C), and pass to the condenser via (7), after passing through the drop separator device (8). heater enters (9) and exits (10).

 Two prototype devices have already been built, with capacities of 50 and 200 liters / hour of water evaporated on summarily decanted grape must.

 Starting from low densities, of the order of 1.09 or 220Brix, we could, without difficulty reaching 1.32, or g50Brix which corresponds to 8tri0 grams / liter of sugar. The residual pressure, having been maintained at 30 millibars, the evaporation temperature was of the order of 250C. The heating water was at 50 C and that of the condenser at 13 / 150C.

 The nylon threads of the "scraper" devices show no visible wear after a long period of operation.

 It is obvious that the applications of this eva carrier model can be numerous, especially in food and pharmaceutical engineering. It allows to treat sensitive products, at low temperature and over a wide range of viscosities. It seems particularly indicated for capacities evaporation up to a ton of water per hour, the liquid to be evaporated can obviously vary.

 Let us also add that, depending on its evaporative capacity, this equipment comes in a reduced volume; moreover its driving is easy.

Claims (5)

 RLUENDICAT'ONS  1 - Process for the concentration of a solution, by evaporation. characterized by a succession of actions applied to the solution to be treated, passing into a dispersed state in a cascade of vacuum chambers. Forced to travel through their internal, hot surface in a thin layer and turbulent regime, it is the site of intense evaporation of the water (or solvent) of constitution. 2 - evaporator apparatus for implementing the method according to claim 1, composed of a series of identical enclosures, of elliptical section, juxtaposed vertically and coaxially, one on top of the other, communicating with one another by wide circular openings. All of this stacking is contained in a cylindrical envelope through which a heat transfer fluid circulates, and maintained under high vacuum. 3 - Apparatus according to claim 2, with a concentrically rotating axis, and on which are fixed as many turbines and son devices, there are enclosures in the stack. The centrifugal effect disperses the treated solution. 4 - Apparatus according to claims 2 and 3, wherein various son devices allow by friction of these on the inner walls of the speakers, scraping them and keep a high coefficient of heat transmission. 5 - Apparatus according to claims 2, 3 and 4, which has in its upper part, on the suction of the vapors released, a cylindrical chamber, provided with a drop separator, fixed on the axis mentioned above, which allows them to be collected and reintroduced into the evaporation chamber.